Hydraulically actuated articulated members



NOV 13,1956 J. MERCIER ETAL 2,770,297

HYDRAULICALLY ACTUATED ARTICULATED MEMBERS Filed Jan. 19. 1954 2Sheets-Sheet l ATTORNEYS Nov. 13, 1956 J. MERCIER Erm. 2,770,297

HYDRAULICALLY ACTUATED ARTICULATED MEMBERS Filed Jan. 19. 1954 2Sheets-Sheet 2 .TL s l -f A? I FEV ATTO R N EYS United States Patent OHYDRAULICALLY ACTUATED ARTICULATED MEMBERS Application January 19, 1954,Serial No. 404,896 23 Claims. (Cl. 1GO-18S) This invention relates tothe art of hydraulically actuated articulated members and moreparticularly to hydraulically actuated hatch covers.

As conducive to an understanding of the invention, it is noted thatmar-ine hatch covers generally comprise a plurality of extremely heavyrectangular panels which lie in a horizontal plane. The use of a derrickor hoist to lift the individual panels out of the hatchway and to stackthem in position away from the hatch so that it is open to receivecargo, is a burdensome and time-consuming chore that requires manypersonnel and delays the loading and unloading of a ship.

Where a plurality of hingedly connected pairs of hatch covers are usedto cover the hatchway, and hydraulic means are used to open thehatchway, if one of the pairs of hatch covers folds to substantiallyvertical position before movement of the other pair or pairs of hatchcovers, the folded pair may tilt about its hinge causing considerablestress and strain on such hinge and disengagement of the rollers of thehatch doors from the guide rails of the hatch opening along which theynormally ride.

It is Iaccordingly among the objects of the invention to provide a hatchcover which with but a simple manipulation by a crew member withoutundue effort on his part, may readily be moved from closed to openposition and vice-versa without the need of a derrick or hoist.

Another object of the invention is to provide a hydraulic system foractuating a plurality of pairs of hatch covers, which will insure thatall of the pairs of hatch covers will open substantially half way beforeany one pair is moved to vertical position thereby preventing unduestrain and stress on hinges, rollers and the like.

Another object of the invention is to provide a hydraulic system that issimple, compact, having but few moving parts that are not likely tobecome out of order, that is eicient in operation, requiring but aminimum quantity of fluid under pressure for opening and closing of thehatchway with resultant low power consumption.

According to one aspect of the invention, a pair of hydraulic units, oneof which is double acting and the other single acting, are mounted inopposed relation rcspectively in each of a pair of hingedly connectedmembers and the plungers of such hydraulic units react against opposedsides of a reaction member idly mounted between such hingedly connectedmember on a pivot rigid with one of said members, in such manner thatthe hinged members may be moved from one extreme position to anotherextreme position. Desirably the effective area of the plunger of thesingle acting unit is greater than that of the double acting unit sothat it will first operate to move the hingedly connected member.

According to another aspect of the invention, a pair of hydraulic unitsare mounted in opposed relation respectively in each of a pair ofhingedly connected members and the plungers of such units react againstopposed sides of a reaction member idly mounted between the hingedlyconnected members on a pivot rigid with one ice of said members, in suchmanner that the hinged members may be moved from one extreme position toanother. The equipment is designed so that the perpendicular distancesto the hinge connection, from lines representing the initial `directionof the forces applied by the plungers to points on opposed sides of thereaction member will differ.

In the accompanying drawings in which are shown one or more of variouspossible embodiments of the several features of the invention,

Fig. l is a fragmentary perspective view of the deck of a ship showing ahatchway with the hatch doors in open position,

Fig. 2 is :a transverse sectional view of a pair of hatch door panelswith the associated hydraulic vactuating system,

Fig. 3 is a perspective View of a hinge,

Fig. 4 is a plan view of a reaction member,

Fig. 5 is a diagrammatic view of a plurality of pairs of hatch covers,

Figs. 5a and 5b are diagrammatic views of the plurality of pairs ofhatch covers in various posit-ions,

Figs. 6 and 7 are charts illustrating the operation of the equipment.

Referring now to Fig. l of the drawings, in the illustrative embodimentshown, the deck 11 of a ship has a conventional hatch opening l2 havinga supporting rail 13 along each side. A plurality of substantiallyrectangular hatch covers 14 are provided of length such that the ends ofeach cover may rest on the rails 13 when in hatch :closing position asshown in Fig. 2.

As illustratively shown, two pairs of hatch covers 14 are provided,although it is to be understood that but a single pair or more than twopairs could be used. The two pairs of hatch covers, designated A and B,each has two panels A-1, A-Z; B-l, B-2 respectively with the panel A-lbeing pivotally connected to the adjacent end 15 of the opening 12 bymeans of hinge members 16. The adjacent lower edges 17 of the paneis ofeach pair of covers are connected 'as by means of hinges 18 and theadjacent upper edges of the panels A-2 and B-l are also connected as byhinges 19. The panels A-2 and B-1 at each corner of their commonlyconnected edges and each [corner of the free edge of panel B-2,desi-rably mount rollers 16 which ride along the beams 13 to facilitateopening and closing of said panels.

As the mechanism to actuate each of the pairs of covers is identical,only that associated with the cover A will be described in detail. Thehinge 18 connecting the adjacent lower edges 17 of the panels A-l andA-2 has two hinge plates 20 (Fig. 3) which are affixed to beams 21extending the length of each of the panels adjacent the edges 17 as isclearly shown in Fig. 2. Although but a single hinge 13 could connectthe two panels A-l and B-l, in the illustrative embodiment shown, twohinges 18 are provided, one near each of the ends of the panels.

The hinges may be of the type having two spaced fingers 22 on the hingeplate affixed to one of the panels i. e., panel A1 straddled by twospaced fingers 23 on the hinge plate affixed to the other panel,I with apintle or pin 2li extending through such fingers in conventional manner.The central finger which is generally provided to fit between the twospaced fingers 22 of the first hinge plate is desirably eliminated inthe present construction and in its place a reaction member, preferablya plate 25 is provided.

The plate 25 (Fig. 4) may be substantially triangular in shape and hasan opening 26, 27 and 23 at each of its corners. The plate 25 isdesirably positioned in a vertical plane with one of its corners betweenthe two spaced 3 lingers 22 of the rst hinge plate so that the pin 24extends freely through the opening 26 as is shown in Fig. 2.

Means are provided coacting with the reaction plate 25 to move thepanels A-1 and A-2 from the closed position shown in Fig. 2 in whichthey lie in side by side relationship in -a horizontal plane, to openposition as shown in Fig. l, in which they extend substantially parallelto each other in a vertical plane.

To this end, a pair of opposed actuating means are providedillustratively hydraulic units 31 and 32 mounted respectively in panelsA-1 and A-2. Although the opposed units 31, 32 m-ay be mounted in anysuitable manner, the rear end of each of the units is desirablypivotally mounted as at 33 to a beam 34 extending longitudinally of theassociated panel approximately midway between its side edges. The outerends of the reciprocable plungers 35, 36 of units 31 and 32 respectivelyare pivotally connected to the reaction plate 25 by means of pins 33, 39extending through the outer end of the plungers and the openings 27 and2S respectively. The hydraulic unit 31 is of the single acting type andhas a cylinder 41 with but a single control port 42, preferably at oneend. The hydraulic unit 32 is of the double acting type having a piston43 affixed to its plunger 36 and slidably mounted in the bore of thecylinder 44 of such unit. The cylinder 44 has a pair of control ports 45`and 46 positioned on each side of the piston 43.

ln the illustrative embodiment shown, as both hydraulic units areconnected to the same source of iiuid under pressure, to insure thatonly one of the units will operate at a time, the effective areas of thereciprocating members of each of the units differ. Thus, for example,the effective area of the plunger 35 of the single lacting hydraulicunit 31 is greater than the effective area of the piston 43 of thedouble acting unit 32. Desirably, a stop 51 is aixed to the end of theplunger of the single acting unit 31 and a stop 52 is aixed to the endof cylinder 44 of double acting unit 32 to limit the outward movement ofthe plungers from their associated cylinders.

Although the hydraulic units may be supplied with fluid under pressurein any suitable manner, in the illustrative embodiment herein shown, thefluid pressure system comprises a reservoir 55 connected by line 56 to apump 57 driven by motor M. The outlet of pump 57 leads through a one-waycheck valve S and is connected by line 59 to a pressure accumulator 61,such as for example, the Olaer accumulator manufactured by GreerHydraulics, Inc. of Brooklyn, New York. rlfhe line 59 also leads to theinlet port 63 of a selector valve 64. The valve 64 in addition to port63 has a discharge port 65 connected to the reservoir 55 by line 66 andtwo control ports 67 and 68 connected respectively by line 69 to controlports 42 and 46 of the hydraulic units and by line 71 to control port 45of unit 32. The selector valve is of the conventional three-way typehaving an off position and two operating positions. In one of theoperating positions, the inlet port 63 and control port 67 are connectedso that uid under pressure may llow into the control ports 42 and 46 ofthe hydraulic units and the discharge portv 65 and control port 68 areconnected so that the fluid will flow from hydraulic unit 32 to thereservoir. In the other operating position the inlet port 63 and thecontrol port 68 are connected so that fluid under pressure may flow intothe control port 45 of hydraulic unit 32 and the discharge port 65 isconnected to control port 67 so that iluid will flow from the controlports 42 and 46 of the two hydraulic units back to the reservoir 55.

Operation To illustrate the operation of the equipment it will first bedescribed with respect to a system having but a single pair of hatchcovers such as A-l, A-2 shown in Fig. 1. To ready the system foroperation, with valve 64 in off position, the accumulator 61 is rstcharged by energizing motor M. When the pressure in the accumul-ator hasreached a desired value, the motor M will be de-energized byconventional pre-set pressure control means (not shown) associatedtherewith.

To operate the hatchway, the selector valve 64 is actuated so that theinlet port 63 is connected to control port 67 and discharge port 65 isconnected to control port 68. As a result, lluid under pressure willflow from the accumulator 61 through ports 63, 67, line 69 into theports 42 and 46 of the hydraulic units 31 and 32. As the effective areaof the plunger 35 is greater than that of the piston 43, and also due tothe friction in the portion of line 69 between units 31 and 32, theplunger 35 will first move to the right from the position shown in Fig.2. As a result, the reaction plate 25 will be pivoted in a clockwisedirection about the hinge pin 24 and a resultant force directed upwardlywill be provided with the result that the two panels A-l, A-2 will moveupwardly from their normal horizontal position. As the force exerted bythe plunger 35 of unit 31 is greater than that exerted by the plunger 36of the hydraulic unit 32, the latter unit will not function at thistime. Consequently, it is only the force exerted by the plunger 35 thatserves to lift the panels. During the movement of the plunger 35 ofhydraulic unit 31, the plunger 36 of the hydraulic unit 32 will not moveand will be in the position shown in Fig. 2. When the plunger 35 hasreached the limit of its stroke, i. e., when stop 51 abuts against theend of the cylinder 41, the panels will have been pivoted each to a 45degree angle, i. e., the angle between the panel at the pivot point 24will be approximately 90 degrees.

At this time, since the plunger of the hydraulic unit 31 is incapable offurther movement, as its stop 51 is against the end of cylinder 4l, thetluid under pressure in line 69 will then cause the plunger 36 ofhydraulic unit 32 to move to the left As no movement will be imparted tothe plunger of hydraulic unit 31 due to the greater area thereof againstwhich the force of the uid under pressure is exerted, the movement ofthe plunger of hydraulic unit 32 reaching against plate 25 will furtherpivot the panels, until the piston 43 of the hydraulic unit 32 abutsagainst the stop 52 of the cylinder 44 at which time the doors will bein substantially vertical position.

In Fig. 7, the curve T which follows a sinusoidal law, represents thetorque required to lift the panels from horizontal to vertical position.

As the hydraulic unit 32 does not function to lift the panels until theyare at a degree angle with respect to each other, i. e., are half Wayopen, at which time considerably less torque is required to lift thepanels than when they were in the original horizontal position, thedimensions of the hydraulic unit 32 may be considerably smaller thanthat of the hydraulic unit 31. As a result, the quantity of fluid underpressure required to be forced into the hydraulic unit 32 for fullstroke is much less than that required for unit 31. Since less fluid isused than would be required if both hydraulic units were the same size,less power is required to recharge the accumulator which of course,entails considerable saving.

With the panels in vertical position, to move the panels to closedposition it is merely necessary to set the selector valve so that theinlet port 63 is connected with control port 68 and the discharge port65 is connected with control port 67. As a result fluid under pressurewill flow from the pressure accumulator through line 71 into portV 45 ofthe hydraulic unit 32.

With the panels in vertical position, but little force is required tomove them slightly away from vertical and thereafter the panels, due totheir weight, require little or no force to move them to closedposition. Consequently, the relatively small hydraulic unit 32 isadequate to start the closing action of the panels and to insure thatthey will move to closed horizontal position.

It is noted that during the first movement of the panels to theirhalf-way position in which only the hydraulicV unit 3l is functioning,due to the fact that no fluid is owing through the line 7l there will beno back pressure and hence the liquid in the pressure accumulator neednot be under as great a pressure as would be necessary if there was backpressure in the system which had to be overcome during initial movementof the panels. Although there is back pressure `when the secondhydraulic unit 32 is operating, due to the ilow of uid through port d5and the associated line 7l, as the pressure on the liquid reactingagainst the piston i3 need not be as great as that required to initiallymove the panels, the maximum pressure required in the accumulator tomove the doors from half-way position to fully open position still isbelow that to which it is normally charged.

In addition to providing a great saving in power to open the panels, theprovision of the single acting hydraulic unit in conjunction with adouble acting unit insures that in a system in which there are aplurality of pairs or" panels of the above type connected to each other,all of the pairs will first assume half-way open position before any onepair attains a vertical position. Consequently, no one pair of panelswill have to travel a considerable distance before the entire set ofpanels is fully open, with the harmful eiect that the vertical pair ofpanels traveling a considerable distance may tilt in one direction orthe other causing undue strain on the hinge connection between such pairof panels and the adjacent pair and also causing the rollers associatedwith the vertical pair of panels to move off their tracks and possiblyJam.

Referring to Fig. 5 of the drawings, with two pairs of panelsillustrated, when fluid under pressure is applied to line 69, forexample, as the single acting units 31 are of greater size than thedouble acting units 32, one o1' the other of the units 3i would rstoperate to raise its associated pair of panels, Once one or the other ofthe units 3l operated, as the pair of panels associated therewithrequire less and less torque to open as they are moved from horizontalposition, the pair of panels trst moving away from horizontal positionwould otter less resistance to the tiow of uid in line 69 and hence suchpair of panels would continue their upward movement and substantially nofluid would tlow `into the other hydraulic units. As the hydraulic unit31 associated with panel A-l in addition to the load of the panels A-iand A-Z would also have to drag the panels B-l and B-2 toward the hingeld before the panels A-l and A-Z could move upwardly, the hydraulic unit3l of panel B-l would in all probability first operate.

As previously described with respect to the panels shown in Fig. 2, thehydraulic unit 3l of panel B-l would move to the limit of its strokecausing the panels B-l and B-2 to move upwardly until an angle ofapproximately 90 degrees was provided between such two panels asdiagrammatically shown in Fig. Sa.

At this time, due to the fact that the area of `the hydraulic unit 3l.of panel A-l is greater than that of the hydraulic units 32, thehydraulic unit 31 would then function and the panels A-l and A-2 wouldthen move to assume an angle of 90 degrees therebetween drawing thepanels B-ll and B-2 toward the hinge 16.

At this time, the doors would be in the position shown in Fig. 5b. Sincethe hydraulic units 31 had reached the limit of their strokes, one orthe other of the hydraulic units 32 would next be actuated. In view ofthe available pressure in the system, both of the hydraulic units 32would operate, but as the hydraulic unit 32 of panel A-2 must also pullthe panels B-l and 13 2, the hydraulic unit 32 of panel B-2 wouldoperate at a much greater rate and would cause the panels B-l and B-2 tomove into vertical position.

As the hydraulic unit 32 of panel A-2 has also been operating at thistime, when the panels B-ll and B-Z reach vertical position, the panelsA-1 and A-2 would have approached such position and consequently the Cil6 panels B-l and B-2 would have but little distance to travel invertical position before the panels A-l and`A-2 also had reached thisposition and all panels were fully open in vertical position.

As a result, tilting of any of the pairs of panels is substantiallyprecluded and hence there is no likelihood of injury to the hingeconnection or dislodgement of the rollers from the guide rails.

For most eicient operation of the hatch doors, it is desired that thehydraulic actuating system utilize as little fluid under as low apressure as possible.

The curve of the torque T (Fig. 7) required to lift a pair of hatchcovers may be represented by the following formula:

F=Pressure eiective area of plunger D=R sine a R=distance from pivotalconnection of reaction plate to point of application of force theretoa=the angle between the extension of a line from the pivotal connectionof the reaction plate through the point of application of force theretoand a line representing the direction of application of said force tothe reaction plate Thus D=the perpendicular distance of the pivotalconnection of the reaction plate from a line representing the initialdirection of the force applied to a point on one side or" the reactionplate and D can be varied by changing either R or a Hence, the eicientoperation afforded by the use of a single acting hydraulic unit may beenhanced by proper selection of the angles a (X and Y in Fig. 6) and thedistance R1 and R2 shown in Fig. 6.

ln the curve of Fig. 7 the torque T necessary to lift the panels ismaximum when the pair of panels is in horizontal position and minimumwhen they are in vertical position, i. e., when the two panels havemoved a total of 180 degrees.

With a given force F1, it is apparent from Fig. 6 that the greater theangle X up to degrees, the greater the distance D1 and hence the greaterthe torque T1 which will be available to move the hatch covers.

With the maximum possible D1 provided. by the largest angle X that willstill permit full movement of the panels to vertical position, due totheir physical dimensions, the effective area A1 of the plunger ofhydraulic unit 31 and the pressure P1 are selected so that the productof the three parameters D1, P1 and A1 will initially provide the desiredtorque T1 to lift the panels from horizontal position, i. e., a torquegreater than T maximum in Fig. 7, yet which` will still be suicient tomove the panels to their half-way position indicated at M in Fig. 7.

The curve T1, representing the torque F1D1 is shown in Fig. 7.

When the pair of panels has attained approximately half-way position,only the hydraulic unit 32 will then operate.

From the chart shown in Fig. 7, it is apparent that less torque is nowrequired to move the panels to vertical position. l

As P1 is predetermined, based upon the pressure required to actuatehydraulic unit 31, the values of A2 of the piston of hydraulic unit 32land D2 are selected so that a minimum of fluid under pressure isrequired to provide the necessary torque T2 to move the panels toVertical position. Thus, angle Y is made as large as possible, (but lessthan 90 degrees) and A2 as small as possible.

A typical curve T2 representing the torque FzDz provided by hydraulicunit 32 is shown in Fig. 7.

By the selection of the appropriate angles X and Y, each of which isless than 90 degrees, and distances Ri and R2, the pressure in thesystem and the quantity of fluid required to be forced from theaccumulator can be kept to a minimum. As a result, a minimum of power isrequired to charge the accumulator with attendant saving in cost. Wherethe system uses no accumulator but a pump only to supply the fluid underpressure, the power required to actuate the pump motor will be kept to aminimum.

With the equipment above described, dependable actuation of a pair ofhatch covers is provided with low power consumption and where aplurality of pairs of covers are used, injury to the hinge connection issubstantially precluded.

As many changes could be made in the above equipment, and manyapparently widely different embodiments of this invention could be madewithout departing from the scope of the claims, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

Having thus described our invention, what we claim as new and desire tosecure by Letters Patent of the United States is:

l. A system of the character described comprising a pair of pivotallyconnected members, a hydraulic unit in each of said members mounted inopposed relation, each of said units having a reciprocable plunger, areaction member, a pivotal mount for said reaction member, one end ofeach of said plungers being connected to the reaction member on opposedsides thereof respectively, whereby upon movement of said plungerstoward each other, said connected members will be rotated about theirpivotal mount, the effective area of one of the plungers against whichfiuid under pressure will react to move said plunger toward the otherplunger being greater than the effective area of said other plungeragainst which fluid under pressure will react.

2. A system of the character described comprising a pair of pivotallyconnected members, a hydraulic unit in each of said members mounted inopposed relation, each of said units having a reciprocable plunger, areaction member, a pivotal mount for said reaction member, one end ofeach of said plungers being connected to the reaction member on opposedsides thereof respectively, whereby upon movement of said plungerstoward each other, said connected members will be rotated about theirpivotal mount, one of said hydraulic units being of the single actingtype and the other of the double acting type, the effective area of thesingle acting unit against which fluid under pressure will react beinggreater than the effective area of the double acting unit.

3. A system of the character described comprising a pair of pivotallyconnected members, a hydraulic unit in each of said members, mounted inopposed relation, each of said units having a reciprocable plunger, areaction member, a pivotal mount for said reaction member extendingparallel to the pivotal mount of said pair of members, one end of eachof said plungers being connected to the reaction member on opposed sidesthereof respectively, whereby upon movement of said plungers toward eachother said connected members will be rotated about their pivotal mount,the eective area of one of said hydraulic units against which fiuidunder pressure will react being greater than the effective area of theother hydraulic unit.

4. A system of the character described comprising a pair of pivotallyconnected members, a reaction member, a pivotal mount for said reactionmember, means carried by each of said members operatively connected tosaid reaction member on opposed sides thereof respectively,

to exert force against said reaction member to rotate said connectedmembers about their pivotal mount, the perpendicular distance to thepivotal mount of the reaction member from a line representing thedirection of application of force thereto by one of said means differingfrom the perpendicular distance to the pivotal mount of the reactionmember from a line representing the direction of application of forcethereto by the other of said means.

5. A system of the character described comprising a pair of pivotallyconnected members, a reaction member, a pivotal mount for said reactionmember extending parallel to the pivotal mount of said pair of members,a hydraulic unit carried by each of said pair of members, mounted inopposed relation, each of said units having a reciprocable plungeroperatively connected at one end to said reaction member on opposedsides thereof respectively to exert force against said reaction memberto rotate said connected members about their pivotal mount, theperpendicular distance to the pivotal mount of the reaction member froma line representing the direction of application of force thereto by theplunger of one of said hydraulic units being greater than theperpendicular distance to the pivotal mount of the reaction member froma line representing the direction of application of force thereto by theplunger of the other hydraulic unit.

6. The combination set forth in claim 5 in which the effective area ofthe hydraulic unit against which fluid under pressure will react toeffect movement of one of said plungers is greater than the effectivearea of the other hydraulic unit against which uid under pressure willreact to effect movement of the other of said plungers.

7. The combination set forth in claim 5 in which the effective areaagainst which fluid under pressure will react to effect movement of theplunger of the first of said hydraulic units is greater than theeffective area against which fluid under pressure will react to effectmovement of the plunger of the other hydraulic unit.

8. The combination set forth in claim 5 in which one of said hydraulicunits is of the single acting type and the other of the double actingtype.

9. The combination set forth in claim 5 in which said first hydraulicunit is of the double acting type and the other hydraulic unit is of thesingle acting type.

10. The combination set forth in claim 5 in which said first hydraulicunit is of the double acting type and the other hydraulic unit is of thesingle acting type and the effective area against which fluid underpressure will react to effect movement of the plunger of the singleacting unit is Igreater than the effective area against which fluidunder pressure will react to effect movement of the plunger of thedouble acting unit.

ll. A system of the character described for controlling access to ahatchway comprising a plurality of pairs of pivotally connected panelsadapted to extend over said hatchway to close the latter, adjacentpanels of each pair being pivotally connected to each other, each of thepairs of said pairs of panels having a hydraulic unit mounted therein inopposed relation, each of said units having a reciprocable plunger, areaction member for each of the pairs of panels, a pivotal mount foreach of said reaction members, one end of each of the plungers beingconnected to opposed sides respectively of the associated reactionmember, whereby upon movement of said plungers toward each other, thepanels of each pairv will be rotated about their respective pivotalmounts, the effective area of one of the plungers against which fiuidunder pressure will react to move said plunger toward the other plungerbeing greater than the effective area of said other plunger againstwhich fluid under pressure will react.

l2. A system of the character described for controlling access to ahatchway, comprising a plurality of pairs of .pivotally connected panelsadapted to extend over a hatchway to close the latter, adjacent panelsof each pair being pivotally connected to each other, a reaction memberfor each ot the pairs of panels, a pivotal mount for each of saidreaction members, means carried by cach of said panels operativelyconnected to the associated reaction member on opposed sides thereofrespectively, to exert force against said reaction member to rotate thepairs of panels about their pivotal mounts, the perpendicular distanceto the pivotal mount ot each reaction member from a line representingthe direction of applica tion of torce thereto by one of the associatedmeans differing from the perpendicular distance to the pivotal mount ofsaid reaction member from a line representing the direction ofapplication of force thereto by the other associated means.

13. A system of the character described tor controlling access to asubstantially rectangular hatchway, comprising a plurality of pairs ofpivotally connected substantially rectangular panels adapted to extendover said hatchway to close the latter, adjacent panels ot each pair fbeing pivotally connected to each other, the panel of one of said pairsadjacent one end of the hatchway being hinged to the latter, each of thepanels of said pairs of panels having a hydraulic unit mounted thereinin opposed relation, each of said units having a reciprocable plunger, areaction member for each of the pairs ot panels, a pivotal mount foreach of said reaction members, one end of each of the plungers beingconnected to opposed sides respectively of the associated reactionmember, whereby upon movement of said plungers toward each other, thepanels of each pair will be rotated about their respective pivotalmounts, the eiective area of one of the hydraulic units associated witheach pair of panels, against which fluid under pressure will react beinggreater than the effective area of the other associated hydraulic unit.

14. The combination recited in claim 13 in which the perpendiculardistance to the pivotal mount of each reaction member from a linerepresenting the direction ot force thereto by the plunger of one of theassociated hydraulic units is greater than the perpendicular distance tosaid pivotal mount from a line representing the direction of applicationof force to the reaction member from the plunger of the other associatedhydraulic unit.

l5. A system of the character described for controlling access to asubstantially rectangular hatchway comprising a pair of substantiallyrectangular pivotally connected panels adapted to extend over thehatchway to close the latter, means hingedly connecting one of thepanels to one end ot the hatchway, a hydraulic unit in each of saidpanels, mounted in opposed relation, each of said units having areciprocable plunger, a reaction member, a piv otal mount for saidreaction member, one end ot each of said plungers being connected to thereaction member on opposed sides thereof respectively, whereby uponmovement of said plungers toward each other, said panels Will be rotatedabout their pivotal mount and the hinge connection, the effective areaof one of the plungers against which iiuid under pressure will react tomove said plunger toward the other plunger being greater than theetective area of said other plunger against which tluid under pressurewill react.

16. The combination set forth in claim 15 in which the pivotalconnection for said panels and the pivotal mount for the reaction memberare identical.

17. The combination set forth in claim 15 in which the pivotalconnection for said panels and the pivotal mount for the reaction memberare identical and the reaction member comprises a substantiallytriangular plate pivoted 4at one corner on its pivotal mount andpivotally connected at its two other corners to the ends of theassociated plungers.

18. The combination recited in claim 15 in which one end of each of thehydraulic units is pivotally connected to the associated panel betweenits side edges.

19. A system of the character described comprising a pair of pivotallyconnected members, a reaction member, a pivotal mount for said reactionmember, means carried by each of said members operatively connected tosaid reaction member on opposed sides thereof respectively, to exertforce against said reaction member to rotate said connected membersabout their pivotal mount, the angle defined between a line representingthe direction of original application of force by one of said means andthe extension or" a line from the pivotal mount of said reaction memberthrough the point of application of such force ditlering from the .angledeiined between a line representing the direction of originalapplication of force by the other of said means and the extension of aline from the pivotal mount of said reaction member through the point ofapplication of such last named force.

2i). The combination recited in claim. 19 in which said means comprisestwo units, one capable of exerting greater force than the other.

21. The combination recited in claim 20 in which the unit capable ofexerting greater force is associated with the smaller angle.

22. A system of the character described comprising a pair of pivotallyconnected members, `a reaction member, a pivotal mount for said reactionmember, means carried by each of said members operatively connected tosaid reaction member on opposed sides thereof respectively, to exertforce against said reaction member to rotate said connected'membersabout their pivotal mount, the product of the force originally exertedby one of said means and the perpendicular distance to the pivotal mountof the reaction member from a line representing the direction ofapplication of such force thereto by the associated means being greaterthan the product of the force originally exerted by the other of saidmeans and the perpendicular distance to the pivotal mount of thereaction member from a line representing the direction of application ofsuch second force thereto.

23. The combination recited in claim 22 in which the angle eiinedbetween a line representing the direction of original application offorce by said rst means and the extension of a line from the pivotalmount of said reaction member through the point of application of suchforce is less than the angle defined between a line representing thedirection of original application of the second force by the other ofsaid means and the extension of a line from the pivotal mount of saidreaction member through the point of application of such second force,

References Cited in the iile of this patent UNITED STATES PATENTS2,491,261 Greer etal Dec. 13, 1949

